This invention relates to connector assemblies used to provide an interface between a remote light source and the end portions of fiber optic light cables and the like and to the method of making such connector assemblies.
It is generally known to provide connector assemblies on the end portions of fiber optic light cables to provide an interface between a remote light source and the optical fiber end portions for transmitting light from the remote light source through the cables. Such connector assemblies commonly include a metal tube or ferrule made of brass or other malleable material that is crimped around the optical fiber end portions to provide a compressive force on such end portions causing such end portions to be tightly pressed together. In addition, a buffer material made for example of Teflon is interposed between the metal ferrule and optical fiber end portions to protect the fibers against damage by the metal ferrule. Connector assemblies of this general type are disclosed for example in U.S. Pat. Nos. 4,885,663, 4,907,132 and 5,042,900, the entire disclosures of which are incorporated herein by reference.
A drawback to such connector assemblies is that heretofore it has been very difficult to obtain the most effective packing of the fiber optic strands allowing for maximum inception of light into the fiber optic light cables and minimum damage to the individual fibers.
The present invention relates to connector assemblies for fiber optic light cables that are formed by press fitting a plastic tube having a predetermined inner diameter into a metal tube or ferrule and then crimping the connector assemblies onto the end portions of the optical fibers to create a compression force on the optical fibers to maintain the optical fiber end portions densely packed together. The inner diameter (ID) of the plastic tube is determined by the following formula to maintain the most effective packing of the optical fiber end portions allowing for maximum inception of light into the end portions and minimum damage to the individual fibers:       ID    =          Fiber      ⁢              xe2x80x83            ⁢      Diameter      xc3x97                                    Number            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            Fibers                                Packing            ⁢                          xe2x80x83                        ⁢            Factor                                ,
where the fiber diameter can be any diameter from 0.010xe2x80x3 to 0.120xe2x80x3 and the Packing Factor (P.F.) can be any number between 0.92 and 0.75.
Determining the inner diameter of the plastic tube using this formula allows one size plastic tube to be used to make connector assemblies for multiple fiber optic bundles. The plastic tube buffers the optical fiber end portions from the metal ferrule thus preventing damage to the optical fiber end portions. At the same time, the plastic tube is made stiff enough to prevent the end portions of the individual optical fibers from sinking into the plastic tube and blocking light. Preferably the coefficient of expansion and contraction of the plastic tube is similar to that of the optical fibers to minimize walking of the connector assemblies on the optical fiber end portions every time the light source is turned on and off.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter more fully described and particularly pointed out in the claims, the following description and annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.